RFR: 8279008: G1: Calculate BOT threshold on-the-fly during Object Copy phase [v2]

[Albert Mingkun Yang]

> Simple change of unifying BOT logic for PLAB and direct allocation during GC.
> 
> Test: tier1-6; no difference observed while running BigRamTester, SPECjbb2015

Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:

  Update src/hotspot/share/gc/g1/g1BlockOffsetTable.inline.hpp
  
  Co-authored-by: Thomas Schatzl <59967451+tschatzl at users.noreply.github.com>

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6916/files
  - new: https://git.openjdk.java.net/jdk/pull/6916/files/962d3398..1242f947

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6916&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6916&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6916.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6916/head:pull/6916

PR: https://git.openjdk.java.net/jdk/pull/6916